Measurement system

ABSTRACT

A measurement system includes: a sensor wire comprising an insertable portion configured to be inserted in a blood vessel of a patient&#39;s body; a sensor disposed at the insertable portion at a distal end of the sensor wire, wherein the sensor is configured to provide an output indicative of a temperature in the blood vessel of the patient&#39;s body, when inserted inside the blood vessel of the patient&#39;s body; and a transceiver unit configured to transfer information related to the output of the sensor to an external communication module using a frequency hopping technique. The transceiver unit comprises a housing adapted to be connected to a proximal end of the sensor wire and configured to remain external to the patient&#39;s body.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/930,540, filed on Jul. 16, 2020, now U.S. Pat. No. 11,234,650, whichis a continuation of U.S. application Ser. No. 16/401,156, filed May 2,2019, now U.S. Pat. No. 10,736,573, which is a continuation of U.S.application Ser. No. 15/865,519, filed on Jan. 9, 2018, now U.S. Pat.No. 10,314,488, which is a continuation of U.S. application Ser. No.15/415,271, filed Jan. 25, 2017, now U.S. Pat. No. 9,888,848, which is adivisional of U.S. application Ser. No. 14/950,847, filed Nov. 24, 2015,now U.S. Pat. No. 9,585,566, which is a continuation of U.S. applicationSer. No. 14/218,017, filed Mar. 18, 2014, now U.S. Pat. No. 9,220,461which is a divisional of U.S. application Ser. No. 13/847,226, filedMar. 19, 2013, now U.S. Pat. No. 8,698,638, which is a continuation ofU.S. application Ser. No. 13/444,487, filed Apr. 11, 2012, now U.S. Pat.No. 8,410,940, which is a continuation of U.S. application Ser. No.12/771,167, filed Apr. 30, 2010, now U.S. Pat. No. 8,174,395, which is acontinuation-in-part of U.S. application Ser. No. 11/601,853, filed Nov.20, 2006, now U.S. Pat. No. 7,724,148, the disclosures of which areincorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates to a transceiver unit and a communicationunit for a pressure measurement system for measuring a physiologicalvariable in a body.

BACKGROUND

In many medical procedures, medical personnel need to monitor variousphysiological conditions that are present within a body cavity of apatient. These physiological conditions are typically physical innature—such as pressure, temperature, rate-of-fluid flow—and provide thephysician or medical technician with critical information as to thestatus of a patient's condition. Obviously, the manner by which thesetypes of parameters are measured and monitored must be safe, accurateand reliable.

One device that is widely used to monitor such conditions is the bloodpressure transducer. A blood pressure transducer senses the magnitude ofa patient's blood pressure, and converts it into a representativeelectrical signal. This electrical signal is then supplied to a vitalsigns monitor that displays, records or otherwise monitors the magnitudeof the patient's blood pressure.

Traditionally, a blood pressure transducer has consisted of a pressureresponsive diaphragm that is mechanically coupled to piezoresistiveelements connected in a Wheatstone Bridge-type circuit arrangement. Whenthe diaphragm is placed in fluid communication with a body cavity (suchas within the arterial or venous system), pressure induced deflectionsof the diaphragm cause the resistive elements to be stretched (orcompressed, depending on their orientation). According to well-knownprinciples, this alters the resistance of the elements in a manner thatis proportional to the applied pressure. The magnitude of the appliedpressure can thus be detected by applying an excitation power signal(usually in the form of a voltage) to the inputs of the Wheatstonebridge circuit, and by simultaneously monitoring the bridge outputsignal. The magnitude of that signal reflects the amount by which thebridge resistance has changed, according to Ohm's law.

Typically, an electrical cable connects the Wheatstone bridge portion ofthe transducer sensor to a transducer amplifier circuit contained withinthe vital signs monitor. This amplifier circuit supplies the excitationpower signal to the Wheatstone bridge, and simultaneously monitors thebridge output signal. The excitation power signal is typically in theform of a voltage and, depending on the monitor type and manufacturer,can have varying magnitudes and formats, both time-varying (sinusoidal,square-waved and pulsed) and time independent (DC).

According to the principles under which conventional Wheatstone bridgetransducers operate, transducer amplifier circuits in most patientmonitors have been designed to expect a sensor output signal having amagnitude that is proportional to the magnitude of the excitation powersignal and also proportional to the magnitude of the sensed pressure.Because different monitors supply excitation power signals havingdifferent magnitudes and/or frequencies, standard proportionalityconstants have been developed. These proportionality standards allow anysensor to be readily adapted for use with any patient monitor alsocalibrated to adhere to the proportionality standard.

Several benefits are provided by this compatibility. Blood pressuretransducers could be used interchangeably with patient monitors fromdifferent manufacturers. As such, medical personnel were not required toselect a specific transducer for use with a specific monitor. Further,hospital investments in pre-existing patient monitors were preserved,thereby reducing costs. As a consequence, vital signs monitors adheringto these proportionality standards have achieved almost universalacceptance in medical environments.

However, the blood pressure transducers and monitors that have beenpreviously used, and the resulting standards that have evolved, are notwithout drawbacks. For instance, the sensors used in these systems weretypically positioned external to the patient's body and placed in fluidcommunication with the body cavity via a fluid-filled catheter line.Pressure variations within the body cavity are then indirectlycommunicated to the diaphragm by way of fluid contained with thecatheter line. As such, the accuracy of such systems has suffered due tovariations in hydrostatic pressure and other inconsistencies associatedwith the fluid column.

In response to this problem, miniaturized sensors using advancedsemiconductor technologies have been developed. These types oftransducer sensors are extremely accurate, inexpensive and still utilizethe well known Wheatstone bridge-type of circuit arrangement, whichtypically, at least partly, is fabricated directly on a siliconediaphragm. Further, the sensors are sufficiently small such that theycan actually be placed on the tip of an insertable guide wire and residedirectly within the arteries, tissues or organs of the patient. Thiseliminates the need for a fluid line because the fluid pressure iscommunicated directly to the transducer diaphragm. As a result, thesesensors—often referred to as guide wire-tipped transducers—provide amuch more accurate measurement of the patient's blood pressure.

Unfortunately, the electrical configurations of these miniaturizedsemiconductor sensors are not always compatible with the transduceramplifiers in existing patient monitors. For instance, the miniaturizedsensors often cannot operate over the entire range of excitation signalmagnitudes and frequencies found among the various types of patientmonitors. Thus, they cannot be connected directly to many of the patientmonitors already in use. To be used with such existing monitors, aspecialized interface must be placed between the sensor and the monitor.Such an arrangement necessitates additional circuitry on the interfaceand, because existing monitors have been designed to provide onlylimited amounts of power, the additional circuitry may require anindependent source of electrical power. As a consequence, use of thenewer miniaturized sensors often adds cost and complexity to the overallsystem.

In addition, because of the above limitations, these sensors must oftenbe configured to generate an output signal which is proportional to thepressure sensed, but that is not related to the excitation signal,supplied to the sensor by the monitor, in a way that is directly usableby the physiology monitor, e.g. the sensitivity may be different. Asdiscussed, this does not conform with the electrical format required bythe many monitors that are commercially available and already inwidespread use. As such, the newer sensors can only be used withspecific monitor types, thereby requiring additional, and oftenredundant, equipment to be purchased. This is especially undesirablegiven the cost sensitivities so prevalent in today's health careenvironment.

The Association for the Advancement of Medical Instrumentation (“AAMI”)has defined power requirements for physiology monitors and in particularthe input/output connector to a sensor wire assembly must comply withthe standard set by American National Standards Institute (“ANSI”)/AAMIBP22-1994 (referred to as “BP22” in the following).

According to the BP22-standard an input/output connector arranged at theproximal end of a five line connector cable includes a pair ofdifferential output signal lines. The output signal lines are driven bya sensor adapting circuitry's output digital to analog converters(discussed further herein below). The differential output signal, by wayof example, operates at 5 μV/mmHg/V_(EXC). An operation range of −150μV/V to 1650 μV/V therefore represents a sensed pressure range of −30 to330 mmHg. An exemplary resolution (minimum step) for the differentialoutput signal is 0.2 mmHg.

U.S. Pat. No. 5,568,815 discloses an interface circuit for interfacing asensor to a patient monitor. The interface circuit includes a powersupply circuit that receives an excitation power signal generated by thepatient monitor, and derives therefrom unregulated and regulated supplyvoltages for use by the electrical components on the interface circuit.Further, the power supply circuit generates an appropriate sensorexcitation signal. The interface circuit further includes receivingcircuitry for receiving a sensor output signal generated by the sensor.A scaling circuit then scales that signal into a parameter signal thatis proportional to the physiological condition detected by the sensor,and that is also proportional to the excitation power signal generatedby the patient monitor.

An obvious drawback of the device of U.S. Pat. No. 5,568,815 is that, inorder to connect the sensor to the monitor, a separate additional unitin the form of the interface circuit is required.

Furthermore, in U.S. Pat. No. 5,568,815 is also discussed the issues ofhaving an electrically conducted device such as a pressure transducerconnected both to a patient and to an electronic monitoring instrument.Great care must then be taken to insure that electrical currents atstandard power line frequencies cannot flow from the patient, throughthe transducer connection, and to ground. An additional risk occurs inpatents which are undergoing defibrillation while having an electricallyconductive transducer attached.

Thus, the insulation problem has previously been addressed by usingfiber-optics or opto-isolator devices to achieve the connection with themonitor device.

The physical connection between the sensor device and the monitor devicemust be seen in the total set-up during pressure measurements which alsomay include other instruments involved having its cables or connectionswhich may result in a complex and non-user-friendly environment for theuser. In this connection also the sterilisation issue must be mentioned;in the systems according to the prior art there are physicalconnections, irrespectively if it is for electrical or opticalcommunication purposes, directly to the monitoring device, which requirethat the entire system must be sterilized and eventually disposed.

A solution to the insulation problem is to use wireless communication totransmit the measure values from the sensor to the monitoring device.

In U.S. Patent Application Publication No. 2006/0009817, assigned to theassignee of the present application, a system and a method for obtaininga wireless communication of physiological variables are disclosed. Thesystem comprises a control unit providing a communication interfacepreferably for radio frequency communication using a carrier signal,which is generated by a monitoring device. The control unit is arrangedwith a modulator for modulating the carrier signal with a signalrepresenting a measured physiological value received from a sensordisposed in the body. Thus, the function of the control unit isdependent upon the generation of a carrier signal from an external unitin order to be able to transfer the measured variables.

Furthermore, the above-mentioned U.S. patent application Publicationonly indicates that the control unit may be attached to the core wire ofthe guide wire via a connection wire using a suitable connector means,such as a crocodile clip-type connector, or if the connection wire isomitted, directly connecting the core wire to the control unit by asuitable connector. The connector is not further discussed in the aboveapplication.

Thus, in the complex environment of an operating room and taken thedifferent drawbacks of the prior art solutions, the general object ofthe present invention is to achieve an improved device being moreuser-friendly and reliable than the presently available systems.

SUMMARY

The above-mentioned object is achieved by the present inventiondescribed herein.

In particular the present invention obviates the need of a physicalconnection between the patient and the monitoring device by arranging areliable wireless link connection between a an easy-to-use transceiverunit and a communication unit, and in particular that the measuredpressure data is generated by the transceiver unit and transferred as adata stream. The transceiver unit, when receiving pressure sensor datafrom the pressure sensor, is adapted to self-contained, directly or at alater time, generate a wireless transmission of pressure data to thecommunication unit without using any carrier wave from the communicationunit or any other unit.

The communication unit is adapted to be connected to an external deviceby a standard input/output connector in accordance with an establishedstandard or in accordance with relevant parts of an establishedstandard, e.g. BP22 or USB, as briefly discussed in the backgroundsection.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described indetail in the following with reference made to accompanying drawings, inwhich:

FIG. 1 shows an exemplifying sensor mounted on a guide wire inaccordance with prior art and which is applicable herein.

FIG. 2 schematically illustrates a measurement system according to thepresent invention.

FIG. 3 shows a block diagram schematically illustrating a transceiverunit according to a preferred embodiment of the present invention.

FIG. 4 shows a block diagram schematically illustrating a transceiverunit including a sensor signal adapting circuitry according a preferredembodiment of the present invention

FIG. 5 shows a block diagram schematically illustrating a communicationunit according to an alternative embodiment of the present invention.

FIG. 6 schematically illustrates a male connector according to anembodiment of the present invention.

FIG. 7 schematically illustrates a female connector according to anembodiment of the present invention.

FIG. 8 schematically illustrates a measurement system according toanother embodiment of the present invention.

FIG. 9 schematically illustrates a transceiver, a communication unit,and an external device according to an embodiment of the presentinvention.

FIG. 10 schematically illustrates a transceiver, a communication unit,and an external device according to an embodiment of the presentinvention.

FIG. 11 schematically illustrates a measurement system according to anembodiment of the present invention.

FIG. 12 schematically illustrates a measurement system according to anembodiment of the present invention.

FIG. 13 schematically illustrates a transceiver, a communication unit,and an external device according to an embodiment of the presentinvention.

FIG. 14 schematically illustrates an external device according to anembodiment of the present invention.

FIG. 15 schematically illustrates a measurement system according to anembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the prior art, it is known to mount a sensor on a guide wire and toposition the sensor via the guide wire in a blood vessel in a livingbody to detect a physical parameter, such as pressure or temperature.The sensor includes elements that are directly or indirectly sensitiveto the parameter. Numerous patents describing different types of sensorsfor measuring physiological parameters are owned by the applicant of thepresent patent application. For example, temperature could be measuredby observing the resistance of a conductor having temperature sensitiveresistance as described in U.S. Pat. No. 6,615,067. Another exemplifyingsensor may be found in U.S. Pat. No. 6,167,763, in which blood flowexerts pressure on the sensor which delivers a signal representative ofthe exerted pressure.

In order to power the sensor and to communicate signals representing themeasured physiological variable to an external physiology monitor, oneor more cables or leads for transmitting the signals are connected tothe sensor, and are routed along the guide wire to be passed out fromthe vessel to the external physiology monitor, conventionally viaphysical cables. In addition, the guide wire is typically provided witha central metal wire (core wire) serving as a support for the sensor and(optionally) also as an electrical connection to the sensor, and asurrounding tubing. Hence, a guide wire typically comprises a core wire,leads and a protective tubing.

FIG. 1 shows an exemplifying sensor mounted on a guide wire inaccordance with conventional design which is applicable for the presentinvention. The sensor guide wire 101 comprises a hollow tube 102, a corewire 103, a first spiral portion 104, a second spiral portion 105, ajacket or sleeve 106, a dome-shaped tip 107, a sensor element or chip108, and one or several electrical leads 109. The tube 102 has typicallybeen treated to give the sensor guide construction a smooth outersurface with low friction. The proximal end of the first spiral portion104 is attached to the distal end of the hollow tube 102, while thedistal end of the first spiral portion 104 is attached to the proximalend of the jacket 106. The proximal end of the second spiral portion 105is connected to the distal end of the jacket 106, and the dome-shapedtip 107 is attached to the distal end of the second spiral portion 105.The core wire 103 is at least partly disposed inside the hollow tube 102such that the distal portion of the core wire 103 extends out of thehollow tube 102 and into the second spiral portion 105. The sensorelement 108 is mounted on the core wire 103 at the position of thejacket 106, and is connected to an external physiology monitor (notshown in the FIG. 1 ) via the electrical leads 109. The sensor element108 comprises a pressure sensitive device in the form of a membrane (notshown in the FIG. 1 ), which through an aperture 110 in the jacket 106is in contact with a medium, such as blood, surrounding the distalportion of the sensor guide wire 101.

FIG. 2 is a schematic overview illustrating the application of thepresent invention.

The pressure measurement system according to the present inventioncomprises a pressure sensor wire with a pressure sensor to measurepressure inside a patient, and to provide measured pressure data to anexternal device. The pressure sensor wire is adapted to be connected, atits proximal end, to a transceiver unit adapted to wirelesslycommunicate via a radio frequency signal with a communication unitarranged in connection with an external device (also referred to asexternal physiology monitor), in order to transfer measured pressuredata to the external device.

The external device may be a dedicated device, i.e. a patient monitoringdevice, preferably provided with a monitor, or a PC (personal computer)provided with relevant software and external connections to receive andto process the measured data from the pressure measurement system. Oneexample of a dedicated device applicable herein is disclosed in U.S.Pat. No. 6,565,514. A preferred embodiment of the present invention mayhave the external device be a standard cath lab monitor system; however,other external devices are contemplated, such as a mobile unit or adevice where the data is sent directly to a mobile unit. Such mobileunits may include, for example, a mobile phone, an iPhone, and aBlackberry with specific applications.

FIG. 3 shows a block diagram schematically illustrating the transceiverunit according to the present invention. As shown in FIG. 1 thetransceiver unit is adapted to be connected to the proximal end of apressure sensor wire provided, at its distal end, with a pressure sensorto measure pressure inside a patient. Preferably, the transceiver unitcomprises a sensor signal adapting circuitry 2, which will be describedin greater detail below, a communication module 4, connected to theadapting circuitry 2, that will handled the wireless communication withthe communication unit.

In particular during the specific situation where a number oftransceiver units are arranged to communicate with one communicationunit, also single-directional communication may be used, primarily forsake of obtaining a reliable communication link.

The measured pressure data is independently generated by the transceiverunit and transferred as a data stream to the communication unit at aprescribed frequency range (in the case where the communication signalis a radio frequency signal), to be further discussed below.

According to a preferred embodiment the communication signal is a radiofrequency signal, and that embodiment will be described in detail below.

Furthermore, according to the preferred embodiment the radio frequencysignal transmits the data as data packets, i.e. in a digital form. Theradio frequency transmission may, as an alternative, be an analogue datatransmission.

Generally the communication signal may be an electromagnetic wavesignal, e.g. a radio frequency signal, an infrared signal, or a lightsignal.

According to alternative embodiments the communication signal may be anywirelessly transmitted signal, e.g. an ultrasound signal or a magneticsignal. A person skilled in the art may easily adapt the describedsystem, i.e. the transceiver unit and communication unit, to use any ofthe mentioned communication signals.

The preferred embodiment where the communication signal is a radiofrequency signal will now be described in detail. Although thetransceiver unit and the communication unit are described in connectionwith the preferred embodiment it should be appreciated that relevantfeatures would be equally applicable in case any of the alternativecommunication signals is used.

With references to FIGS. 2 and 3 , the communication module is connectedto an antenna 6. In the figures the antenna is illustrated as protrudingoutside the transceiver unit but may, as in an alternative, beintegrated into the housing of the transceiver unit. The pressure sensorwire is adapted to be inserted into an elongated aperture 8 of thetransceiver unit. The aperture is at its inner surface provided with anumber of electrical connecting surfaces (not shown) to be connected toelectrode surfaces at the proximal end of the pressure sensor wire wheninserted into the aperture 8. The transceiver unit is further providedwith wire fastening means (not shown) to firmly fixate the wire whencorrectly inserted into the aperture.

According to a preferred embodiment the transceiver unit is adapted toreceive the proximal end to the pressure sensor wire having an outerdiameter of 0.35 mm, i.e. the inner diameter of the elongated aperture 8is slightly larger than 0.35 mm.

U.S. Pat. No. 5,938,624 relates to a male connector (shown in FIG. 6 )with a continuous surface for a guide wire which preferably is appliedas a male connector for the proximal end of the pressure sensor wire tobe connected to a transceiver unit according to the present invention.The male connector 200 includes a core wire 201, and conductive members202 spaced apart longitudinally along the core wire. A continuousinsulating material 203 is disposed between the guide wire and theconductive members and the insulating material having an outer surfacecoextensive with outer surfaces of the conductive members.

As mentioned above, the transceiver unit according to the presentinvention is provided with a fastening means to fasten the proximal endof the pressure wire to the transceiver unit. The fastening means may bea female connector of the type disclosed in U.S. Pat. No. 6,428,336(shown in FIG. 7 ) into which a male connector of the kind describedabove may be inserted and secured to provide electrical contact with thecontact surfaces of the male connector. The female connector 300comprises an insulating hollow housing 301 containing three hollowcontact members 302 a, 302 b, and 302 c to make contact with theconductive members of the male connector. At the distal end of thefemale connector, the fastening means 303 for securing the maleconnector in the female connector is provided.

The male connector of the pressure sensor wire used in respect of thepresent invention is preferably compatible with the female connectordisclosed in U.S. Pat. No. 6,428,336.

When the pressure sensor wire is fixated to the transceiver unit theunit may be used as a “handle” when guiding the pressure sensor wireduring insertion into a patient. Preferably the transceiver unit isprovided with guiding means 10, e.g. in the form of one or manyelongated ribs on the outer surface of the transceiver unit, or byproviding the transceiver unit with a roughened surface.

The pressure sensor wire may be fixated to the transceiver unit suchthat as the transceiver unit is rotated along its longitudinal axis thesensor wire is also rotated, which often is necessary in order to guidethe sensor wire during the insertion procedure. As an alternative, thesensor wire is fixated to the transceiver unit in such way that thesensor wire may be rotated in relation to the transceiver unit. Therotation of the sensor wire is then achieved by firmly holding thetransceiver unit by one hand and by rotating the sensor wire by theother hand.

The transceiver unit is preferably activated and initiated via anactivation button 12 arranged at the housing of the unit. The activationbutton is preferably mechanically activated.

According to an alternative embodiment the transceiver unit is activatedand initiated when the proximal end to the sensor wire is correctlyinserted into the unit. This may e.g. be achieved by arranging a pushbutton at the bottom of the cavity into which the pressure wire isinserted.

According to another alternative embodiment the transceiver unit isactivated and initiated when electrical connections are establishedbetween corresponding electrical contact surfaces of the female and maleconnectors, respectively.

According to still another alternative embodiment the transceiver unitis activated and initiated by a remote signal generated from thecommunication unit in response of a command from the monitoring device.

The transceiver unit comprises energy means to energize the transceiverunit and the circuitry of the connected pressure sensor wire. The energymeans is preferably a battery or a capacitor that e.g. may be includedin the sensor signal adapting circuitry.

The pressure sensor wire as well as the transceiver unit are preferablydisposable units that must be able to sterilise prior use.

According to an alternative embodiment of the invention, in order tofurther improve the user-friendliness of the transceiver unit, anattachment means is provided at the housing of the unit. The attachmentmeans may be in the form of a strap, a clip or a hook, i.e. anymechanical attachment means enabling the transceiver unit to bestationary during use.

FIG. 4 shows a block diagram schematically illustrating a sensor signaladapting circuitry applicable in the present invention and preferablyintegrated into the transceiver unit.

With references to FIGS. 1 and 2 the pressure sensor wire comprises asensor element for measuring the physiological variable and to generatea sensor signal in response of said variable, a guide wire having saidsensor element at its distal portion, preferably close to its distalend, and adapted to be inserted into the body in order to position thesensor element within the body. The transceiver unit comprises thesensor signal adapting circuitry (FIG. 4 ), wherein the sensor signal isapplied to the adapting circuitry that is adapted to automaticallygenerate an output signal, related to the sensor signal, in a formatsuch that the measured physiological variable is retrievable by anexternal device. According to a preferred embodiment the sensor signaladapting circuitry comprises a programmable sensor conditioning means, acalibration means, being a storage means into which calibration data maybe supplied, stored and altered, e.g. an electrically erasableprogrammable read-only memory (EEPROM), energy means and an outputamplifying means.

The programmable sensor conditioning means is preferably a PGA309programmable analog sensor conditioner (available from Texas InstrumentsInc.) specifically designed for bridge sensors.

According to a preferred embodiment of the present invention theexternal device supplies the sensor signal adapting circuitry with areference voltage value wirelessly via the radio link and thecorresponding voltage is applied from the energy means in thetransceiver unit. By considering the signal standard with which theexternal device complies, which is indicated to the adapting circuitryby means of the reference voltage, and the actual value of the physicalparameter measured by the sensor element, the signal adapting circuitrywill process the signal from the sensor element such that an adaptedsignal in accordance with the standard expected by the monitor may bewirelessly sent back to the external device.

The communication between the transceiver unit and the communicationunit is preferably performed in a so-called license-free radio frequencyinterval.

The term “license-free radio” refers to the permission granted bygovernment agencies to allow multiple radios to operate in a specifiedfrequency band at one time. These license-free bands are known as theISM (Industrial, Scientific and Medical) bands.

The two most commonly used ISM bands are referred to as the 900 MHz andthe 2.4 GHz bands. Both permit the use of license-free Spread Spectrumradios within them. For the most part, the 900 MHz band is used in theAmericas. The 2.4 GHz band is used (with differing power constraints)throughout most of the world. While there are some differences betweenthe characteristics of the two bands, the 900 MHz band typically allowsfor higher power and longer distance transmissions while the 2.4 GHzband, with its wider bandwidth, allows for higher data rates. In Europe,the 869 MHz and 433 MHz bands are also classified as ISM bands and Chinahas opened the 220 MHz band to license-free radios.

In an embodiment of the present invention a frequency band of 2.4 GHz(2.2-2.6 GHz) is used. A typical communication distance would be lessthan 10 meters.

In order to achieve a secure transmission of the sensor values from thetransceiver unit to the communication unit, preferably a frequencyhopping technique is used, e.g. by use of Bluetooth. The frequencyhopping technique is well-known to persons skilled in the art of radiocommunication, and will therefore only briefly be described herein.

The transceiver unit comprises a first communication module to handlethe radio frequency communication with the communication unit that isprovided with a second communication module.

When the pressure sensor wire has been inserted into the transceiverunit and the communication unit is connected to the external device thesystem is ready for use.

By pressing the activation button on the transceiver unit it isactivated and will then try to establish a radio link connection withthe communication unit. This is preferably performed by a conventionalhandshake procedure in order to identify the transceiver unit. Thesystem is now ready to receive measured sensor data.

Pressure sensor values measured at specific times, exemplary designated1, 2, 3, 4, 5, etc., are respectively designated P1, P2, P3, P4, P5,etc, are applied to the communication module of the transceiver unit.These values are preferably transmitted in packets of three values perpacket, e.g. P1, P2 and P3, forming packet P1P2P3; the next packetcomprises values P2, P3 and P4 forming packet P2P3P4, and the nextpacket comprises values P3, P4 and P5 forming packet P3P4P5, etc.Consecutive packets are transmitted at different frequencies, i.e.packet P1P2P3 is sent at a first frequency F1, packet P2P3P4 is sent ata second frequency F2, and packet P3P4P5 is sent at a third frequencyF3. Next packet would have been P4P5P6 and would have been sent at thefirst frequency F1, etc. This type of transmission is called a frequencyhopping transmission. Thus, each pressure sensor value will then be sentthree times, which increases the transmission security.

The packets received by the communication unit will then be unpacked bythe second communication module in the communication unit and formattedsuch that the pressure values may be applied to the external device inaccordance with the required signal standard, e.g. BP22 signal standardor USB standard, where they will be made available, e.g. on a displaymeans.

As mentioned above the programmable sensor conditioner means ispreferably implemented by means of a PGA309 programmable analog sensorconditioner. The PGA309 is particularly designed for resistive bridgesensor applications and contains three main gain blocks for scalingdifferential input bridge sensor signals. Hence, as discussed in theabove, a signal representing the measured physiological variable may beadapted such that a signal in a format expected by the monitor isprovided. This signal format is determined by the reference voltagesupplied to the sensor signal adapting circuitry and the actual value ofthe signal measured by the sensor. The PGA309 can be configured for usewith an internal or external voltage reference. According to the presentinvention, an internal reference voltage of e.g. +2.5V is supplied tothe PGA309 from the energy means.

Thus, the conditioner means generates an analog output voltage signalrelated to the sensor signal such that the measured physiologicalvariable, i.e. the pressure, may be retrieved by the external device.

Since each sensor element is an individual item with its owncharacteristics, each sensor assembly comprises a calibration means,preferably an electrically erasable programmable read-only memory(EEPROM) which contains individual calibration data obtained duringcalibration of the sensor element performed for each individual sensorwire assembly. The calibration is performed in connection withmanufacture of the pressure sensor wire. Calibration data takes intoaccount parameters such as voltage offsets and temperature drift, etc.

The bridge pressure sensor is preferably energized from the PGA309 viaan excitation voltage V_(EXC), generated by the PGA309 circuit. As analternative the pressure sensor may be energized from a separate energysource, e.g. a battery or a capacitor means.

For a given excitation voltage V_(EXC), e.g. generated by the PGA309circuit, the output voltage (V_(IN1)−V_(IN2)) of the bridge is a voltageproportional to the pressure applied to the sensor. Hence, the sensoroutput voltage (V_(IN1)−V_(IN2)) (sensor signal in FIG. 4 ) of thebridge is proportional to the pressure applied to the sensor, which fora given pressure will vary with the applied excitation voltage. Thissensor output voltage is preferably compensated for temperaturevariation at the site of the sensor and is applied to the PGA309circuit. The PGA309 circuit also includes gain blocks for adjusting theoutput signal from that circuit and used in addition to the outputamplifying means mentioned above.

According to another preferred embodiment a processing means, preferablya microprocessor (e.g. a PIC16C770 or a nRF24E1, shown with dashed linesin FIG. 4 ) may further be employed to process and adapt the analogoutput voltage V_(OUT) of the conditioned sensor, which output voltageis supplied via the PGA309 programmable analog sensor conditioner. Theanalog output signal from the PGA309 circuit is A/D-converted prior itis applied to the processing means. To adapt the sensor signal to theBP22 signal standard, it may be necessary to process the sensor signalfurther before it is applied to the physiology monitor. For instance amultiplying digital-analog converter (DAC) which possibly is comprisedin the processing means is supplied with digital data (e.g. a 12-bitword) representing the signal measured by the sensor element and thereference voltage. The resulting product is wirelessly sent (afterhaving been filtered) to the external device and is proportional to themeasured sensor signal and the reference voltage.

In the preferred embodiment that has been described herein theadaptation of the sensor signal to the standard, e.g. BP22 signalstandard, is performed in the transceiver unit, and in particular in thesensor signal adapting circuitry. However, this adaptation, in itsentirety or only in parts, may, as an alternative, instead be performedby a corresponding circuitry arranged in the communication unit. Thisembodiment is schematically illustrated in FIG. 5 . The wirelesslytransmitted pressure sensor values would then be in the form of “raw”measured data that would be conditioned by a processing and conditioningmeans in the communication unit in order to be in a correct format to besupplied to the external system according to a prescribed standardformat.

The above embodiment with respect to FIGS. 1-6 relates to the use of apressure sensor wire comprising a pressure sensor element for measuringpressure inside the patient and generating a pressure sensor signal inpressure. Other types of sensors are also contemplated. For example, thesensor wire of FIG. 1 may include a sensor element configured to measureany physiological parameter, such as pressure inside the patient,temperature inside the patient, and blood flow inside the patient. Forexample, one suitable sensor may be a temperature sensor for measuringtemperature by observing the resistance of a conductor havingtemperature sensitive resistance as described in U.S. Pat. No.6,615,067, which is incorporate herein by reference in its entirety.Another suitable sensor may be a sensor for measuring blood flow asdescribed in U.S. Pat. No. 6,167,763, which is incorporated by referencein its entirety, in which the blood flow can be measured eitherelectrically or by using an ultrasonic technique. The electricaltechnique is based on temperature changes incurred by the velocity offlow, cooling being a function of flow rate. More rapid flow yields alarger temperature drop. Other suitable sensors may be found in U.S.Pat. Nos. RE 39,863 and 6,615,667, which are incorporated by referencein their entireties. Further suitable sensors may be blood analytesensors for determine one or more chemical constituents in the blood,such as glucose, oxygenated or deoxygenated haemoglobin, or the like.The information transferred from the communication unit to the externaldevice is then information related to the physiological parameter withthe sensor values being sensor values related to the physiologicalparameter.

Additionally or alternatively, the sensor wire of FIG. 1 may include asensor element configured to measure a non-physiological parameter. Thenon-physiological parameter may be a parameter inside or outside thebody and be generated inside or outside the body. For example, thenon-physiological parameter may be at least one of a magnetic field, amagnetic flux, an X-ray field, and/or an electromagnetic field near thebody; an optical signal near the body; and/or the presence of animplantable, foreign and/or metallic device (such as a stent, needle,pacemaker, drug delivery device, or the like) inside the body. Theinformation transferred from the communication unit to the externaldevice is information related to the non-physiological parameter, andthe sensor values are sensor values related to the non-physiologicalparameter.

With the detection of the non-physiological parameter, the sensorelement can be used for positioning purposes, i.e. to establish theposition of the sensor inside the patient's body using the detection ofthe non-physiological parameter or the detection of a predeterminedlevel of the non-physiological parameter. Such a configuration may bebeneficial when performing physiological measurements (such as, forexample, pressure, temperature, blood flow, blood chemical analysis orthe like) because the exact position of the sensor may be determinedfrom the non-physiological parameter while the physiological measurementis performed. In the example of the optical signal application, a sensorthat is light sensitive would be used in which, when a light is shown onit (for example, in an area just below the skin or through the skin),the sensor would be activated to indicate the position of the sensorelement relative to the light. The detection of the magnetic field,X-ray field, electromagnetic field, and the like may operate similarly.If both physiological and non-physiological parameters are used, FIG. 8shows a suitable configuration would include a sensor wire 401comprising a first sensor element 408A and a second sensor element 408Bdisposed within the insertable portion at the distal end of the sensorwire 401. The other components of FIG. 8 have already been described inrelation to FIG. 1 .

Alternatively, the two sensor elements of FIG. 8 may measure twodifferent physiological parameters or measure two differentnon-physiological parameters. Of course, any number of sensor elementsmay be used such as one, two, three, four, five, or more sensor elementsin which the sensor elements may measure blood pressure; bloodtemperature; blood flow; one or more blood analyte concentrations; amagnetic field; a magnetic flux; an X-ray field; an electromagneticfield; an optical signal; the presence of a metallic instrument,implantable device, or a foreign object (such as, for example, a stent,needle, implantable drug delivery device, pacemaker, etc.), and/or anycombination thereof.

Depending on the number of sensor elements, the transceiver unit of FIG.4 then would have a corresponding number of sensor signal adaptingcircuitry. The sensor signal of each sensor element is then applied toits corresponding adapting circuitry to automatically generate an outputsignal, related to the sensor signal, in a format such that the measuredvariable is retrievable by the external device. One or more of thesensor signal adapting circuitries may comprise a programmable sensorconditioner or sensor conditioning means, a calibrator or calibratingmeans (being a storage device or means into which calibration data maybe supplied, stored and altered, e.g. an electrically erasableprogrammable read-only memory (EEPROM)), an energy device or means andan output amplifier or output amplifying means.

The output signals from the sensor signal adapting circuitries may becommunicated to the communication unit through the pair of communicationmodules, as described above. Of course, it also is contemplated thatmultiple pairs of communication modules may be used, such as, forexample, one pair of communication modules for each type of sensorelement.

Other embodiments are also contemplated for use of the sensor wire withone, two, three, four or more sensors. For example, the sensor signaladapting circuitry 2 is configured to filter, process, and formatsignal(s) received from the sensor wire. The sensor signal adaptingcircuitry 2 may be fully located within the housing of the transceiverunit (see FIG. 3 ) or fully located within the communication unit (seeFIG. 9 ). The sensor signal adapting circuitry 2 may be partiallylocated within the housing (a part of the circuitry is identified as 2′in FIG. 10 ) and be partially located within the communication unit(another part of the circuitry is identified as 2″ in FIG. 10 ). Thesensor signal adapting circuitry 2 may be fully located near thesensor(s) at the distal end of the sensor wire (see FIG. 11 ). Thesensor signal adapting circuitry may be partially located near thesensor(s) at the distal end of the sensor wire (a part of the circuitryis identified as 2′″ in FIG. 12 ) with the other portions of the sensorsignal adapting circuitry being partially located within the housingand/or located within the communication unit. The sensor signal adaptingcircuitry 2 may be fully located at the external device (see FIG. 13 ).The sensor signal adapting circuitry may be partially located at theexternal device (a part of the circuitry is identified as 2″″ in FIG. 14) with the other portions of the sensor signal adapting circuitry beingpartially located within the housing, located within the communicationunit, and/or near the sensor at the distal end of the sensor wire. Whenthe sensor signal adapting circuitry is partially located within thehousing, within communication unit, near the sensor(s) within the sensorwire, or within the external unit, the part of the circuitry may be themajority, a substantial portion, or a fraction of the sensor signaladapting circuitry needed to process the one or more sensors. Forexample, parts of the sensor signal adapting circuitry may be theprogrammable sensor conditioning means, the calibration means, theenergy means, the output amplifying means, or subcomponents thereof inany combination for each sensor, a plurality of sensors, or for all thesensors.

Further embodiments are also contemplated. For example, FIG. 15 shows anembodiment in which the transceiver unit has a communication module thatdirectly communicates with a communication module housed within theexternal device such that the communication unit of FIG. 2 is notneeded. The external device therefore can have a communication moduleand/or have the sensor signal adapting circuitry partially or fullyhoused within the external device. As previously discussed, the externaldevice may be a dedicated device (for example, a patient monitoringdevice, preferably provided with a monitor, or a PC (personal computer)provided with relevant software and external connections to receive andto process the measured data from the measurement system); a standardcath lab monitor system; a mobile unit (such as, for example, a mobilephone, an iPhone, or a Blackberry with specific applications) or adevice where the data is sent directly to a mobile unit.

The present invention is not limited to the above-described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention, which is defined by the appending claims.

What is claimed is:
 1. A measurement system comprising: a sensor wirecomprising an insertable portion configured to be inserted in a bloodvessel of a patient's body; a sensor disposed at the insertable portionat a distal end of the sensor wire, wherein the sensor is configured toprovide an output indicative of a temperature in the blood vessel of thepatient's body, when inserted inside the blood vessel of the patient'sbody; and a transceiver unit configured to transfer information relatedto the output of the sensor to an external communication module using afrequency hopping technique, wherein the transceiver unit comprises ahousing adapted to be connected to a proximal end of the sensor wire andconfigured to remain external to the patient's body.
 2. The measurementsystem according to claim 1, wherein: the sensor comprises a temperaturesensitive resistor, and the output of the sensor is a resistance of thetemperature sensitive resistor.
 3. The measurement system according toclaim 1, further comprising an additional sensor configured to providean output indicative of a magnetic field, a magnetic flux, an X-rayfield, an electromagnetic field, or an optical signal generated outsidethe patient's body.
 4. The measurement system according to claim 1,further comprising an additional sensor configured to provide an outputindicative of a presence of at least one of an implantable device, aforeign device, or a metallic device inside the patient's body.
 5. Themeasurement system according to claim 1, further comprising anadditional sensor configured to provide an output indicative of apressure, a blood flow, or an amount of a blood analyte.
 6. Themeasurement system according to claim 1, wherein the frequency hoppingtechnique is performed by Bluetooth.
 7. The measurement system accordingto claim 1, wherein the transceiver unit further comprises an activatorconfigured to activate and initialize the transceiver unit, wherein thetransceiver unit further comprises a female connector with electricalcontact surfaces, and wherein the activator is configured to activateand initialize the transceiver unit when electrical connections areestablished between the electrical contact surfaces of the femaleconnector and electrical contact surfaces of a male connector at theproximal end of the sensor wire.
 8. The measurement system according toclaim 1, wherein a sensor signal adapting circuitry is disposed withinthe housing and is adapted to filter, process, and format a signalreceived from the sensor wire, and wherein the sensor signal adaptingcircuitry within the housing comprises a storage containing calibrationdata for the sensor wire.
 9. The measurement system according to claim1, further comprising a communication unit housing the externalcommunication module, wherein the communication unit is adapted towirelessly communicate with the transceiver unit via the externalcommunication module.
 10. The measurement system according to claim 1,wherein the sensor wire is fixable to the housing of the transceiverunit such that, as the transceiver unit is rotated along itslongitudinal axis, the sensor wire is also rotated.
 11. The measurementsystem according to claim 1, wherein the housing comprises one or moreelongated ribs on an outer surface of the housing or a roughened surfaceon the outer surface of the housing.
 12. The measurement systemaccording to claim 1, wherein the sensor wire is configured to beinserted into an elongated aperture of the housing of the transceiverunit.
 13. The measurement system according to claim 12, wherein thesensor wire is configured to be inserted into the housing of thetransceiver unit such that the sensor wire is rotatable relative to thehousing of the transceiver unit.
 14. A method of measuring one or moreparameters inside a blood vessel of a patient's body, the methodcomprising: inserting an insertable portion of a sensor wire into theblood vessel of the patient's body, wherein a sensor is disposed at theinsertable portion at a distal end of the sensor wire, wherein atransceiver unit comprising a housing is connected to a proximal end ofthe sensor wire; while the insertable portion is in the blood vessel andthe housing remains external to the patient's body, causing the sensorto provide an output indicative of a temperature in the blood vessel ofthe patient's body; generating a communication signal containinginformation related to the output of the sensor via the transceiverunit; and transferring the communication signal to an externalcommunication module using a frequency hopping technique.
 15. The methodaccording to claim 14, wherein: the sensor comprises a temperaturesensitive resistor, and the output of the sensor is a resistance of thetemperature sensitive resistor.
 16. The method according to claim 14,wherein an additional sensor is disposed at the insertable portion atthe distal end of the sensor wire, the additional sensor beingconfigured to provide an output indicative of a magnetic field, amagnetic flux, an X-ray field, an electromagnetic field, or an opticalsignal generated outside the patient's body.
 17. The method according toclaim 14, wherein an additional sensor is disposed at the insertableportion at the distal end of the sensor wire, the additional sensorbeing configured to provide an output indicative of a presence of atleast one of an implantable device, a foreign device, or a metallicdevice inside the patient's body.
 18. The method according to claim 14,wherein an additional sensor is disposed at the insertable portion atthe distal end of the sensor wire, the additional sensor beingconfigured to provide an output indicative of a pressure, a blood flow,or an amount of a blood analyte.
 19. The method according to claim 14,wherein the frequency hopping technique is performed by Bluetooth. 20.The method according to claim 14, further comprising activating andinitializing the transceiver unit by establishing electrical connectionsbetween electrical contact surfaces of a female connector of thetransceiver unit and electrical contact surfaces of a male connector atthe proximal end of the sensor wire.
 21. The method according to claim14, wherein the sensor wire is fixed to the housing of the transceiverunit such that, as the transceiver unit is rotated along itslongitudinal axis, the sensor wire is also rotated.
 22. The methodaccording to claim 14, wherein the sensor wire is configured to beinserted into an elongated aperture of the housing of the transceiverunit such that the sensor wire is rotatable relative to the housing ofthe transceiver unit.